Not sure I buy a trend towards swerve or “butterfly” or octocanum or h-drive or anything else on Einstein. Swerve drives aren’t new. They’ve been around for more than a decade in FRC. While they are often overrepresented on Einstein compared to their general FRC population, they’re not an overwhelming presence (2 on Einstein seems about historically normal). The largest population of drivetrain in FRC, even among elite competitors, has remained tank drives and I expect that to continue. Even the best teams often favor the advantages in the trade-off of going for a tank drive. What they lose in functionality, they gain back in resources (weight, space, cost, machine time, programming time, driver training time) they can dedicate to other areas. There’s a reason you see teams like 118 using tank drives now, instead of the swerve systems they were famous for in the mid/late-2000s.
The AM14U provided as the KOP drivetrain this year had .140" of drop in the center wheels in both long and square configurations. In a wide configuration, it had no drop.
-Nick
Most teams use anywhere from 1/8-3/16 for 6wd & 8wd robots. Sometimes how much drop you use can be influenced by your wheel choice. For example a 4in Versa wheel from Vex has a “W” like tread pattern that will dig into the carpet fibers while a flat surfaced Colson wheel will not. Last year we used the Versa wheels and needed 3/16in of drop in the long configuration to get a decent turn while this year we used Colsons with 1/8in drop that turned like a dream. We noticed our issue last year when we put the robot on the field and noticed all 6 wheels were touching the carpet.
Depending on what wheels you use you can adjust the drop slightly. What I love about Colson wheels is you can trim them down by shaving down the OD of the wheel. Our drivebase this year was originally designed without a drop (doh!!) in a wide configuration and it turned similar to last year’s long drivebase with 3/16in drop. We shaved down the other wheels by 1/16in to achieve the 1/8in drop and it works great.
I wouldn’t really consider 1625’s 4 wheel tank drive with omnis on the front a ‘butterfly-esk’ drive. It is far more similar to a tank drive, in my opinion.
I think the biggest take away from that list is 8 6 CIM tank drives compared to 4 4 CIM tank drives. 2 to 1 ratio is pretty significant and very new.
Wouldn’t having wheels with different ODs make the center and outside wheels have different speeds? Or is it negligible due to the small change? Also, by shaving 1/16" off wouldn’t that be a 1/16" drop?
Because of the slight change in OD you won’t notice much of a difference. IIRC this is how 233 has dropped their tank drives by just machining slightly smaller wheels.
Depends on how you look at the drop. Because we took 1/16th off of both ends and the robot is weighted towards the back there is 1/8in of clearance between one set of wheels and the floor. Another way people look at it is by how much lower the middle wheel is in relation to the other wheels. I’ve heard it explained both ways.
Ahh ok. I haven’t heard of the first way.
I’ll be home in a couple days and I will try to grab some pictures of what I call our “Bullet Omnis” They are ridiculously triangular and its hilarious.
We can clear this up easily. 4 omni wheels can be called butterfly, to keep the Bees happy and the 148 style drive train can be called Tex Coast Drive like it should be*.
*For those wondering, I’m going to keep depending it be called Tex Coast Drive for the foreseeable future, so you should probably just get on board.
I just think it’s weird that the first drivetrain called butterfly was an articulated traction / omni combination… Then the term enters (vaguely) popular use to refer to the other kinds of articulated drives in 2012-2014… But now we’re changing it because of one team? If all omni was always the intended meaning of butterfly and a traction mode was always an “extra”, then I probably have been misunderstanding the term the whole time.
I can see the challenge of picking a different name for it though. “Omni drive” implies holonomic capability. Perhaps “omni wheel tank” would be more descriptive? Doesn’t exactly bounce off the tongue.
It’s my understanding the original name was given because of the omni only portion of the drive, hence the “float like a butterfly, sting like a bee” phrase. The omni wheels being the “butterfly” and the traction wheels being the “bee”. It became a short hand for the entire articulated drive base but it makes more sense to refer to only the omni portion as “butterfly” since it’s the part that is doing the “floating”.
I don’t think you’re misunderstanding it at all. Texas basically thinks it’s its own country, so they can have their own regional name for a drive train too 
It’s like pop versus soda versus cola-- they’re the same thing, but different regions call it different things. Texas can call it Tex-Coast drive all they want, but Neutrino introduced me to butterfly drive, so I’ll call it that. It doesn’t really matter-- we’re still referring to an articulated omni and traction wheel drive train.
JVN posted why they called it butterfly here.
Are you implying we’re not our own country?
I make no comment as to the statehood or lack thereof of Texas. 
On our 6w tank we have used 1/16" drop center the past 2 years.
That is, the center wheel is 1/16" below the line you draw between the two outer axles, so at any one time, one wheel is 1/8" off the ground. The low drop makes the robot much less wobblier and has no negative effect. We are happy.
I’m 1625’s base driver, and were running a 6 CIM drive with a 16fps free speed (so about 14fps friction speed). Single speed no fancy shifters or anything d: we have 2 DT vex pro 4 inch wheels on the back and 2 Vex pro omnis on the front. I drove a butterfly drive and had a lot of fun doing fancy spins and learned how to control the squirlyness of the drive which helped this year. It helps to get around defense very easily. Thank you everybody for the words of encouragement (: if any more questions pop up feel free to message me!
Don’t go changing drivetrain names because of us. :] Butterfly will always have drop down omnis to me.
My signature has been the same for a number of years. I’ve been calling our drivetrain this year “4 Omni Wheels” which I think has a certain honest ring to it.
If I had to change it though, it would be “Greased Pig Drive” which is what our team compared it to throughout the season. You can push it around but you can’t pin it down.
Cheers, Bryan
I’ve played a lot of defense and I never thought an all 4 omni drive would be so hard to stay on! You guys really made finals on Archimedes interesting:rolleyes: kudos for driving it like you stole it!